linux-kernel - Re: [PATCH] lzo: fix ip overrun during compress.

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Date:   Wed, 28 Nov 2018 06:16:10 +0000
From:   Yueyi Li <liyueyi@...e.com>
To:     Willy Tarreau <w@....eu>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "donb@...uritymouse.com" <donb@...uritymouse.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lzo: fix ip overrun during compress.

Hi Willy,


On 2018/11/28 12:08, Willy Tarreau wrote:
> Hi Yueyi,
>
> On Tue, Nov 27, 2018 at 10:34:26AM +0000, Yueyi Li wrote:
>> It`s possible ip overrun in lzo1x_1_do_compress() when compressed page is
>> point to the end of memory and which virtual address is 0xfffffffffffff000.
>> Leading to a NULL pointer access during the get_unaligned_le32(ip).
> Thanks for this report.
>
> (...)
>> diff --git a/lib/lzo/lzo1x_compress.c b/lib/lzo/lzo1x_compress.c
>> index 236eb21..a0265a6 100644
>> --- a/lib/lzo/lzo1x_compress.c
>> +++ b/lib/lzo/lzo1x_compress.c
>> @@ -17,6 +17,9 @@
>>   #include <linux/lzo.h>
>>   #include "lzodefs.h"
>>   
>> +#define OVERFLOW_ADD_CHECK(a, b)  \
>> +	((size_t)~0 - (size_t)(a) < (size_t)(b) ? true : false)
>> +
> I think the test would be easier to grasp this way :
>
> #define OVERFLOW_ADD_CHECK(a, b)  \
> 	((size_t)(b) >= (size_t)((void*)0 - (void *)(a)))
>
> But the following should be more efficient since we build with
> -fno-strict-overflow :
>
> #define OVERFLOW_ADD_CHECK(a, b)  \
> 	(((a) + (b)) < (a))
Thanks for the suggestion,  I will change it in next version.
> Could you please recheck ?
>
> Thanks,
> Willy

Thanks,
Yueyi